Method of making a gas- and/or vapour discharge tube ready for operation

ABSTRACT

The invention relates to a method of making a discharge tube, for a high pressure sodium vapour discharge lamp, ready for operation by adjusting a heat shield. According to the invention the heat shield consists of a ductile metal strip provided with perforations. The heat shield is adjusted by tearing off a portion of this heat shield on these perforations until the correct temperature is obtained in the operating condition of this discharge tube.

United States Patent [191- 11] 3,79%,37 Timmermans Feb. 5, 1974 [54] METHOD or MAKING-A GAS- AND/0R VAPOUR DISCHARGE TUBE READY FOR OPERATION [76] Inventor: Abraham Timmermans,

Emmasingel, Eindhoven, Netherlands [22] Filed: May 4, 1972 [21] Appl. No.: 250,348

[30] Foreign Application Priority Data May 8, 1971 Netherlands 7106348 [52] US. Cl. 313/44, 313/47 [51] Int. Cl. 1501,] 1/02, HOlj 61/52 [58] Field of Search 313/44, 47

[5 6] References Cited UNITED STATES PATENTS 3,333,132 7/1967 Edris et al 313/47 Primary Examiner-H. K. Saalbach Assistant Examiner-Darwin R. lriostetter Attorney, Agent, or Firm-Frank R. Trifari [5 7] ABSTRACT tions. The heat shield is adjusted by tearing off a portion of this heat shield on these perforations until the correct temperature is obtained in the operating condition of this discharge tube.

6 Claims, 4 Drawing Figures METHOD OF MAKING A GAS- AND/OR VAPOUR DISCHARGE TUBE READY FOR OPERATION The invention relates to a method of making a gasand/or vapour discharge tube ready for operation, in which at least one external part of the wall of the discharge tube is covered by an adjustable heat shield, which is adjusted when the tube is made ready for operation, and furthermore the invention relates to a discharge tube made ready for operation by this method.

A known method of this kind is described, for exam- I ple, in United Kingdom specification 430,437. In this United Kingdom specification 430,437 it is noted that the optimum position andthe optimum shape of the heat shield is first to be determined and this, for example, to bring the lowest temperature of the discharge tube to a desired higher level. It is possible to adjust a heat shield by moving the entire shield to some extent along the discharge tube so that the shield covers a comparatively large or small part of this discharge tube. A drawback thereof is that after the shield is adjusted it is to be secured to the discharge tube again. When, as stated in United Kingdom specification, a heat shield is used which consists of a paint coating including aluminum, the heat shield may only bemodified by either providing more aluminium paint or by removing the paint coating from an already painted portion. Both methods require extra means while great care is to be taken in the use of the paint coating.

An object of the invention is to provide a method of the kind described in the preamble in which on the one hand the drawback of resecurement of a shifted or deformed heat shield ,is prevented and in which on the other hand if some parts of the heat shield remain in their position the displacement of the other parts of the heat shield is very simple.

According to the invention a method of making a gasand/or vapour discharge tube ready for operation,

in which at least one external part of the wall of the dis-.

- charge tube is covered by an adjustable heat shield, and

in which the heat shield is adjusted when the tube is made ready for operation is characterized in that firstly a too large heat shield consisting of ductile metal strip is provided on the wall of the discharge tube and that subsequently parts of this heat shield are removed from said wall, the remaining parts of the heat shield remaining in position. v

An advantage of this method is that making the dis charge tube ready for operation is very simple in this case. The only operation to be carried out is that some pieces of the ductile metal strip have to be removed from the wall of the discharged tube. This may be effected, for example, by hand or by means of simple pliers. In this case such a quantityof the ductile metal strip is removed until the desired condition of the discharge tube is obtained. Resecurement at a later stage of the other parts of the heat shield is no longer necessary in this case. The metal strip may have a width which is equal to the width of the too large heat shield initially provided. It is alternatively feasible that the metal strip is less wide and that a plurality of these metal strips provided side by side or partly across each other constitutes the heat shield. In the latter case the adjustment of the heat shield may consist of winding several turns of this metal strip off the discharge tube.

In an advantageous method according to the invention parts of the heat shield are removed from the ex- 2 ternal wall of the discharge tube by bending these parts of the heat shield.

An advantage of this preferred method is that the entire removal of the superfluous parts of the heat shield from the discharge tube and discarding of this waste material is prevented.

In a further advantageous method according to the invention parts of the heat shield are removed from the external wall of the discharge tube by tearing off these parts.

An advantage of the last-mentioned method is that the heat shield can be adjusted in a very simple manner, for example, by hand.

In a discharge tube which is made ready for operation by means of a method according to the invention the heat shield is preferaby placed at one end of the tube comprising an electrode. These areas near and particularly behind such an electrode often constitute in a discharge tube a coldest spot which is difficult to bring to a slightly higher temperature.

A discharge tube made ready for operation by means of a method according to the invention is preferably provided with a heat shield which has parts bent away from the wall of the discharge tube. This is a discharge tube which is made ready for operation by means of a method in which some heat shield parts are removed, from the wall of the discharge tube, by bending.

The heat shield may have, for example, the same thickness everywhere. It is alternatively feasible that some parts of the heat shield are mechanically slightly weaker than other parts, namely for the purpose of bending away or tearing off parts of the shield from these mechanically weaker portions. Such a mechanically weak portion may be obtained in advance, for example, by notching theheat shield.

An advantageous embodiment of the heat shield is provided with at least one perforation line. A perforation line is understood to means a line which connects a plurality of perforations placed one after the other.

An advatage of this preferred embodiment of the heat shield is that it can be torn off or bent away in accordance with previously determined, clearly visible lines.

Such a perforation line of the heat shield is preferably a closed line encompassng the discharge tube. An advantage of this embodiment is that simple annular pieces can be peeled off the heat shield so that the same quantity of the heat shield can be taken off around the entire circumference of the discharge tube.

In those cases where the discharge tube made ready for operation by means of a method according to the invention has such a quantity torn off the heat shield that also the last portion of the perforation line is used, at least one portion of the surface of this shield has of course a slightly knurled shape which knurls consist of inter alia remaining circumferences of half perforations.

The invention will be described in detail with reference to a drawing in which:

FIG. 1 shows a discharge tube still to undergo an operation according to the invention;

FIG. 2 shows the same discharge tube as in FIG. 1 after having been subjected to a method according to the invention;

FIG. 3 shows one end of the discharge tube before being subjected to a method according to the invention;

FIG. 4 shows the end of the discharge tube as in FIG. 3 after having been subjected to a method according to the invention.

In FIG. 1 reference numeral 1 is a discharge tube intended for a high-pressure sodium vapour discharge lamp. It is, for example, a discharge tube for a lamp described in the United Kingdom Patent specification No. 1,205,871. The length of this discharge tube is approximately 11 cms and the external diameter is approximately 1 cm. The discharge tube is connected to two supply conductors 2 and 3 which are provided on either side of the tube 1. Conductor 2 leads to an internal electrode present within one end of the tube. Conductor 3 leads to an internal electrode present in the other end of the tube 1. The electrodes are not visible. Reference numerals 4 and 5 denote heat shields of metal strip, namely of tantalum having a thickness of 0.05 mm. Metal strip 4 and metal strip Sconstitute too large heat shields for this discharge tube 1. This means that for the size of these heat shields shown in FIG. 1 the lowest temperature of the discharge tube in the operating condition is too high. Reference numerals 6a, 6b etc. denote a row of perforations in the heat shield 4. Reference numerals 7a and 7b etc. denote a second row of perforations in the heat shield 4. Corresponding rows of perforations are also present in the heat shield 5 and are denoted by reference numerals 8a, 8 12 etc. and 9a, 9b etc. The perforation lines 6, 7, 8 and 9 each constitute closed lines encompassing the discharge tube 1. In the embodiment shown each heat shield is initially provided with two perforation Ines. It is of course feasible that a heat shield is initially provided with only one perforation line or with more than two perforation lines.

FIG. 2 shows the situation where an annular strip has been torn off the heat shield 4, namely on the perforation line 7 and in which an annular strip has likewise been torn off the heat shield 5 on the perforation line 9. The other reference numerals given in FIG. 2 of course also relate to the same components as those in FIG. 1.

It may be noted incidentally that it is feasible to form the heat shields of FIGS. 1 and 2 in such a manner that an elongated part thereof extends to beyond the end of the discharge tube 1, which projecting portion constitutes the rasied wall of a cup and in which the end of the discharge tube consitutes the bottom of this cup which is filled with a melting glass. In this manner it may be achieved that a simple seal of this end of the discharge tube can be obtained with this extra part of the heat shield. In this case the commonly used cover at the end of the discharge tube is no loner necessary, but it is sufficient to accomodate only an annular member in the end of the discharge tube.

FIG. 3 shows one end of a discharge tube which is likewise intended for a high-pressure sodium discharge lamp, namely as stated with reference to the test of FIG. 1. The discharge tube of FIG. 3 is denoted by 10. The reference numeral 12 denotes a supply conductor which leads to an electrode (not shown) present in the discharge tube. The reference numeral 14 denotes a heat shield which is provided with a plurality of longitudinal grooves 15, 16, 17 etc. These grooves serve to easily bend parts of the heat shield at a later stage so that these parts no longer engage the wall of the discharge tube 10.

FIG. 4 again shows the discharge tube 10 of FIG. 3. The reference numeral 12 denotes an electric supply conductor and 14 denotes a heat shield. FIG. 4 shows a situation where a lug 20 of the heat shield located between the grooves 16 and 17 (of FIG. 3) is bent upwards. If desired further lugs of this heat shield 14 may be bent away from the discharge tube so that the temperature of this portion of the discharge tube can be adjusted to a slightly different value.

Tearing off and bending away can be effected, for example, by hand or by simple pliers in the described embodiments.

The adjustments of the heat shield in all these embodiments is very simple. It may therefore be used not only for one prototype of the discharge tube but for any discharge tube which is made in the normal manufacture. Thus all these tubes can be adjusted in a simple manner.

What is claimed is:

1. A method of making a gasand/or vapour discharge tube ready for operation, in which at least one external part of the wall of the discharge tube is covered by an adjustable heat shield, which heat shield is adjusted when the tube is made ready for operation, characterized in that firstly a too large heat shield consisting of ductile metal strip is provided on the wall of the discharge tube and that subsequently parts of the heat shield are removed from said wall, the other parts of the heat shield remaining in position.

2. A method as claimed in claim 1, characterized in that parts of the heat shield are removed from the external wall of the discharge tube by bending said parts of the heat shield.

3. A method as claimed in claim 1, characterized in that parts of the heat shield are removed from the external wall of the discharge tube by tearing off said parts.

4. A discharge tube in which at least an external part of the wall is covered by a heat shield which tube is made ready for operation by means of a method as claimed in claim 1, wherein the heat shield is present at an end of the tube and includes an electrode, and wherein the heat shield is provided with parts which are bent away from the wall of the discharge tube.

5. A discharge tube in which at least an external part of the wall is covered by a heat shield which tube is made ready for operation by means of a method as claimed in claim 1, wherein the heat shield is present at an end of the tube and includes an electrode, and wherein the heat shield is provided with at least one perforation line.

6. A discharge tube as claimed in claim 5 wherein the perforation line of the heat shield is a closed line encompassing the discharge tube.

P0405") UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3790837 0 Dated February 5, 1974 Inventor (s) ABRAHAM TIMMERMANS It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 40, "means" should read mean 1 Column 3, line 60, "test" should read -text-- Claim 1, line. 32, "characterized in that" should read --comprising the steps of Claim 1, line 32 "a too should read --p roviding an excessively Claim 11, line 33 delete "is provided" Claim 1, line .34 delete "that" and after "subsequently" insert remov inq a Claim' 1-, line 35 delete "are removed" Claims 2 and" change "characterized in that" to read v wherein'- Signed. and sealed this 21st day of May 1971 (SEAL) Attest: I

EDWARD I I.FLETCHER,JR. MARSHALL BAH-ii Attesting Officer I Commissioner of Patents 

1. A method of making a gas- and/or vapour discharge tube ready for operation, in which at least one external part of the wall of the discharge tube is covered by an adjustable heat shield, which heat shield is adjusted when the tube is made ready for operation, characterized in that firstly a too large heat shield consisting of ductile metal strip is provided on the wall of the discharge tube and that subsequently parts of the heat shield are removed from said wall, the other parts of the heat shield remaining in position.
 2. A method as claimed in claim 1, characterized in that parts of the heat shield are removed from the external wall of the discharge tube by bending said parts of the heat shield.
 3. A method as claimed in claim 1, characterized in that parts of the heat shield are removed from the external wall of the discharge tube by tearing off said parts.
 4. A discharge tube in which at least an external part of the wall is covered by a heat shield which tube is made ready for operation by means of a method as claimed in claim 1, wherein the heat shield is present at an end of the tube and includes an electrode, and wherein the heat shield is provided with parts which are bent away from the wall of the discharge tube.
 5. A discharge tube in which at least an external part of the wall is covered by a heat shield which tube is made ready for operation by means of a method as claimed in claim 1, wherein the heat shield is present at an end of the tube and includes an electrode, and wherein the heat shield is provided with at least one perforation line.
 6. A discharge tube as claimed in claim 5 wherein the perforation line of the heat shield is a closed line encompassing the discharge tube. 